An organic light-emitting device having a resonance structure includes a substrate; a first electrode and a second electrode on the substrate and facing each other; an emission layer between the first electrode and the second electrode; a first hole transport layer between the first electrode and the emission layer; and a second hole transport layer between the first hole transport layer and the emission layer. An electron mobility of the second hole transport layer is 5 times to 100 times greater than an electron mobility of the first hole transport layer, and a thickness of the second hole transport layer corresponds to a resonance distance of a wavelength of emission light of the emission layer.